THE METHOD OF REDUCTION OF AERODYNAMIC FORCES GENERATED IN TURBINE BLADE SEALS

摘要

The distribution of pressure in the seal gaps does not only affect the so called “leakage losses” and the turbine stage overall efficiency but also plays an important role in the generation of aerodynamic forces which may cause self-excited rotor vibrations. The paper describes a chamber seal applied for the reduction of the aerodynamic forces created in shroud seals. This kind of turbine seal was patented and tested. Special attention was paid to the pressure field in the rotor blade shroud clearance in the situation when rotor-stator eccentricity leads to asymmetrical conditions of flows in blade passages and shroud gaps. The investigations into the pressure field in the shroud gap were performed by means of CFD Fluent Code and compared to the results measured on a single-stage air model turbine of the impulse type. The performed experimental investigations and numerical calculations prove that the new turbine seal can reduce pressure forces acting on the stage shroud by about 30%- 50%, depending on the type of the shroud.